Drilling could unearth global forecast

July 03, 2007|By Story by William Mullen Tribune, staff reporter

MCMURDO STATION, Antarctica — Dropped down a hole melted through 267 feet of floating ice, a diamond-toothed drill had to travel another 2,776 feet through seawater before it reached the bottom of an offshore moat in Antarctica and pierced the ocean floor.

There, it began to drill back in time, sending a ropy core sample about 3 inches in diameter back to a derrick built on top of the Ross Ice Shelf.

Nearly a quarter-mile down, the drill bored into sediment that would astonish one of the largest groups of scientists ever assembled in Antarctica. It was a layer more than 300 feet thick of fossilized diatoms, microscopic algae that once bloomed near the ocean surface.

The diatom layer, laid down 2 to 5 million years ago, was evidence that Antarctica has undergone past cycles of warming and cooling. It meant the frozen wastes of the Ross Ice Shelf -- a seemingly permanent slab of ice the size of Spain -- were once open water.

In other times, this information might be of interest only to specialists. But scientists with the Antarctic Geological Drilling project, or ANDRILL, believe the Antarctica of the past can show us what to expect from the warmer world of tomorrow.

In November and December, the ANDRILL team pulled 10 million years of critical climate information out of the Antarctic seabed. The diatom layer was a key prize, representing "a time when ... glaciers were in retreat, a different regime when there was a lot more water in the system," said Reed Scherer, a diatom expert at Northern Illinois University.

In today's terms, "more water in the system" could mean sea levels high enough to put low-lying places like Florida and Bangladesh underwater. If the Ross Ice Shelf again were to shrink or disappear because of higher global temperatures, it could signal very dangerous changes for the rest of the planet, despite its remote place on Earth.

For this reason, ANDRILL is one of the biggest scientific undertakings in the history of Antarctica and a showcase project for the International Polar Year, a major international cooperative research push this year and next that is focusing hundreds of millions of dollars and vast expertise on the Arctic and Antarctic regions. Much of it is related to global warming.

The project brings together 150 scientists from the U.S., New Zealand, Italy and Germany, with the U.S. National Science Foundation providing two-thirds of ANDRILL's $30 million cost. Last year's drilling put 58 geologists, geochemists, volcanologists, sedimentologists, paleomagneticists, paleontologists, petrologists and others "on the ice."

The samples they extracted provide "the best record of time ever established" in Antarctica, said NIU geologist Ross Powell. Now, in a process that will take years, ANDRILL will try to match the new data with much more complete geological histories from the rest of the world.

"We want to relate these warming events with other known world events," said Powell, an expert in glacial sediments.

ANDRILL's slogan is "Drilling back into the future," and Powell reels off some of the questions the project is hoping to answer:

"How did the Antarctic ice sheet react to temperature rises in the past, and how will it react in the future? What's the critical point that triggers changes? Are there tipping points, like water temperature or air temperature that we should be aware of? What was the global picture when this happened before?"

Antarctica was not always as frigid as it is today. Forty million years ago, the Antarctic land mass was connected to the tip of South America and was home to thick vegetation and teeming populations of animals similar to those in Australia.

But when Antarctica became completely detached, a frigid circumpolar current began to spin around it like a giant freezer coil, trapping the continent in a super-cold climate. Glaciers and ice sheets grew up to 3 miles thick, covering 98 percent of Antarctica, which is larger than the U.S. and Mexico combined.

Though the chill has lasted ever since, the amount of ice in Antarctica has grown and shrunk many times during previous global climate changes. The ANDRILL core samples confirm at least 60 warming/cooling cycles in Antarctica in the last 10 million years.

But today's warming trend appears different from those of the past. Most climate experts have come to agree that the pace of change is unusually fast and that the cause seems to be man's activities, primarily the burning of fossil fuels, which releases heat-trapping gases into the atmosphere.

The planet's average annual temperature has risen 1.4 degrees Fahrenheit in the last 100 years, and parts of the Arctic and Antarctic regions have seen much bigger temperature increases, rising as much as 4.5 degrees since the 1950s.